Tertiary recovery operation

ABSTRACT

At the conclusion of a secondary recovery operation after breakthrough of the driving fluid at the production wells, additional injection wells are located between the original injection well and the production well(s), this region usually having a high oil saturation after the drive.

0 United States Patent 11 1 1111 3,834,461 Carlin et al. Sept. 10, 1974 [54] TERTIARY RECOVERY OPERATION 3,332,485 7/1967 Colburn 166/245 3,354,953 11/1967 M 166/274 [75] Inventors: JSePh Hwston; Jseph 3,477,509 11/1969 A233: 166/245 C. Allen, Bellalre, both of Tex. [73] Assignee: Texaco Inc., New York, NY. Primary Examiner-Stephen J. Novosad Assistant Examiner-Jack E. Ebel [22] Flled' 1972 Attorney, Agent, or Firm-T. H. Whaley; C. G. Ries [21] Appl. No.: 317,581

[57] ABSTRACT [52] US. Cl. 166/245, 166/268 [51] Int. Cl E2lb 43/00 At the concluslon of a lq reFovery operano [58] Field of Search 166/245 263 268 272 274 after breakthrough of the driving fluid at the production wells, additional injection wells are located be- [56] References Cited tween the original injection well and the production well(s), this region usually having a high oil saturation UNITED STATES PATENTS after the drive- 3,109,487 11/1963 Hoyt 166/245 3,253,652 5/1966 Connally et al 166/245 8 Claims, 4 Drawing Figures TERTIARY RECOVERY OPERATION FIELD OF THE INVENTION This invention relates generally to the production of hydrocarbons from subterranean hydrocarbon-bearing formations, and more particularly, to a method for increasing the efficiency of the production of hydrocarbons therefrom.

DESCRIPTION OF THE INVENTION In the production of hydrocarbons from permeable subterranean hydrocarbon-bearing formations, it is customary to drill one or more boreholes or wells into the hydrocarbon-bearing formation and produce formation fluids including hydrocarbons, such as oil, through designated production wells, either by the natural formation pressure or by pumping the wells. Sooner or later, the flow of hydrocarbon-bearing fluids diminishes and/or ceases, even though substantial quantities of hydrocarbons are still present in the underground formations.

Thus, secondary recovery programs are now an essential part of the overall planning for exploitation of oil and gas-condensate reservoirs in subterranean hydrocarbon-bearing formations. In general, this involves injecting an extraneous fluid, such as water or gas, into the reservoir zone to drive formation fluids including hydrocarbons toward production wells by the process commonly referred to as flooding. Usually, this flooding is accomplished by injection through wells drilled in a pattern, e.g., the alternating line drive and the more commonly used five-spot pattern, which may be visualized as a special type of staggered line drive pattern wherein the separation of the lines of wells is half the spacing between the individual wells.

When the driving fluid, e.g. water, from the injection well reaches the production wells of a direct line drive and a staggered line drive the areal sweep efficiencies are respectively 57 and 78 percent, and of a five-spot pattern, the areal sweep efficiency is about 71 percent. By continuing production considerably past breakthrough, it is possible to produce more of the remaining upswept portion of the formation although continued injection will not reduce oil saturation much further.

SUMMARY OF THE INVENTION It is an overall object of the present invention to provide an improved recovery procedure involving initially three wells in line as part of a well pattern arrangement for exploiting a hydrocarbon-bearing formation, by locating an additional injection well between secondary injection and production wells in the selected pattern, as determined by model studies or field observation.

A three well group is arranged in line so that the intermediate well is completed for injection and the remaining two wells are completed for production. Flooding is initiated at the intermediate well by injection of a driving fluid, such as water, thereinto and proceeds until breakthrough of the flood front occurs at the production wells, at which time, injection via the intermediate well to maintain flooding may be suspended or terminated. Then, one or more additional injection wells aligned with each other and located between the original injection well and the production wells are drilled into the formation and driving fluid is injected via these additional wells to drive formation fluids toward the production wells. Injection may be resumed at the intermediate well for high injectivity, after injection has been initiated at the additional injection wells. In this manner, the formation areas where the highest oil saturation has been determined to be, usually adjacent the production wells, can be exploited for more complete recovery.

Other objects, advantages and features of this invention will become apparent from a consideration of the specification with reference to the figures of the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 discloses the symbols used in the remaining figures of the drawing;

FIG. 2 illustrates secondary and tertiary phases of a recovery procedure of a direct line drive;

FIG. 3 discloses a staggered line drive, showing the secondary and tertiary phases of a recovery procedure; and

FIG. 4 discloses two units of an inverted five-spot pattern, a special form of a staggered line drive, further illustrating secondary and tertiary phases of a recovery procedure.

The objects of the invention are achieved by the use of additional injection wells located between the original injection and production wells where oil saturation is still above residual oil saturation at breakthrough at the conclusion of secondary recovery procedures.

The specification and the figures of the drawings schematically disclose and illustrate the practice and the advantages of the invention with different well patterns, examples of which have been observed in potentiometric model studies which simulate secondary and tertiary recovery operations. The model studies indicate a sweep-out obtained in an ideal reservoir, although the recovery from an actual sweep-out of a particular field may be greater or less, depending on field parameters.

Throughout the figures of the drawings, the same symbols will be maintained as disclosed in FIG. 1, viz. a solid circle indicates a production well, an open circle with a first quadrant arrow indicates an original injection well, and an open circle with a fourth quadrant arrow, an additional injection well.

Referring to FIG. 2, there is disclosed symbolically a direct line drive in a secondary recovery procedure, wherein the original injection wells are aligned with the production wells. Upon breakthrough of the driving fluid at the production wells, these original injection wells may be put on a standby basis till completion of additional injection wells located between the original injection and the production wells. Then, as driving fluid is injected into the formation via the additional wells, injection via the original wells either may be resumed or terminated. In this figure, the additional injection wells are aligned with the original injection and production wells in the direction of the line drive.

FIG. 3 illustrates a staggered line drive, with the addi tional injection wells being located diagonally between the original injection well and the production wells.

FIG. 4 shows two units of an inverted five-spot pattern, wherein, upon breakthrough of the driving fluid at the comer production wells of each pattern following the injection of secondary recovery driving fluid via the original injection well in the center of the pattern, the additional injection wells are aligned on diagonals production wells.

Ratio of Injection to Sweep Efficiency 7c Production Wells lIILIILa-I As will be apparent to those skilled in the art in the light of the accompanying disclosure, other changes and alterations are possible in the practice of this ininjection well and the production well and after said breakthrough injecting a driving fluid into said additional injection well, and producing formation fluids via said production well.

2. In the recovery method as defined in claim 1,

' maintaining injecting said extraneous fluid via said vention without departing from the spirit or scope thereof.

We claim:

1. A method of producing formation fluids including hydrocarbons from a subterranean hydrocarbon bearing formation of the type wherein said formation is penetrated by an original injection well and a production well and an extraneous fluid is injected into said formation via said original injection well to displace formation fluids including hydrocarbons in said formation toward said production well and said formation fluids including hydrocarbons are produced from said formation via said production well until breakthrough of said extraneous fluid thereat wherein the improvement comprises penetrating said formation with at least one additional injection well located between the original original injection well while injecting a driving fluid into said formation via said additional injection well.

3. In the recovery method as defined in claim 1, discontinuing injection said extraneous fluid via said original injection well while injecting said driving fluid into said formation via said additional injection well.

4. In the method as defined in claim 1, said plurality of wells beingdisposed in a linear pattern, said secondary recovery operation comprising a line drive.

5. In the method as defined in claim 4, the original injection and production wells being disposed in a common row.

6. In the method as defined in claim 4, the original injectionand production wells being disposed in commonrows, additional injection wells being disposed in rows located therebetween.

7. In the method as defined in claim 4, said plurality of wells defining a five-spot pattern.

8. A method of recovering additional petroleum from a subterranean, petroleum containing formation penetrated by at least one original injection well and by at least one production well, said formation having been subjected to secondary recovery of the type wherein an extraneous fluid including water is injected into the orignal injection well to displace petroleum toward the production well comprising penetrating the formation with at least one additional injection well located between the original injection well and the production well, and

injecting an extraneous drive fluid into the additional injection well to displace additional oil toward the production well after extraneous drive fluid injected into the original injection well has reached the production well. 

1. A method of producing formation fluids including hydrocarbons from a subterranean hydrocarbon bearing formation of the type wherein said formation is penetrated by an original injection well and a production well and an extraneous fluid is injected into said formation via said original injection well to displace formation fluids including hydrocarbons in said formation toward said production well and said formation fluids including hydrocarbons are produced from said formation via said production well until breakthrough of said extraneous fluid thereat wherein the improvement comprises penetrating said formation with at least one additional injection well located between the original injection well and the production well and after said breakthrough injecting a driving fluid into said additional injection well, and producing formation fluids via said production well.
 2. In the recovery method as defined in claim 1, maintaining injecting said extraneous fluid via said original injection well while injecting a driving fluid into said formation via said additional injection well.
 3. In the recovery method as defined in claim 1, discontinuing injection said extraneous fluid via said original injection well while injecting said driving fluid into said formation via said additional injection well.
 4. In the method as defined in claim 1, said plurality of wells being disposed in a linear pattern, said secondary recovery operation comprising a line drive.
 5. In the method as defined in claim 4, the original injection and production wells being disposed in a common row.
 6. In the method as defined in claim 4, the original injection and production wells being disposed in common rows, additional injection wells being disposed in rows located therebetween.
 7. In the method as defined in claim 4, said plurality of wells defining a five-spot pattern.
 8. A method of recovering additional petroleum from a subterranean, petroleum containing formation penetrated by at least one original injection well and by at least one production well, said formation having been subjected to secondary recovery of the type wherein an extraneous fluid including water is injected into the orignal injection well to displace petroleum toward the production well comprising penetrating the formation with at least one additional injection well located between the original injection well and the production well, and injecting an extraneous drive fluid into the additional injection well to displace additional oil toward the production well after extraneous drive fluid injected into the original injection well has reached the production well. 